Cations Stiffen Actin Filaments by Adhering a Key Structural Element to Adjacent Subunits

Cations Stiffen Actin Filaments by Adhering a Key Structural Element to Adjacent Subunits

Ions regulate the assembly and mechanical properties of actin filaments. Recent work using structural bioinformatics and site-specific mutagenesis favors the existence of two discrete and specific divalent cation binding sites on actin filaments, positioned in the long axis between actin subunits. Cation binding at one site drives polymerization, while the other modulates filament stiffness and...

Active stiffening of F-actin network dominated by structural transition of actin filaments into bundles

Molecular motor regulated active contractile force is key for cells sensing and responding to their mechanical environment, which leads to characteristic structures and functions of cells. The F-actin network demonstrates a two-order of magnitude increase in its modulus due to contractility; however, the mechanism for this active stiffening remains unclear. Two widely acknowledged hypotheses ar...

Damage to actin filaments by glutaraldehyde: protection by tropomyosin

Reaction of F-actin and the F-actin-tropomyosin complex with 20 mM glutaraldehyde for 19-22 h at 0 degrees C and 25 degrees C results in extensively cross-linked filaments, as judged by sodium dodecyl sulfate (SDS) polyacrylamide gel electrophoresis. Electron micrographs show shorter, more irregular filaments for glutaraldehyde-treated F-actin in the absence of tropomyosin as compared to the pr...

Actin Filaments

The Binding of Divalent Cations to Actin.

Great effort has been spent in recent years on the investigation of certain aspects of actin polymerization, such as the dephosphorylation of adenosine triphosphate during G to F transformation (l-6), the mode of interaction of ATP with actin (i-15), and the role of sulfhydryl, histidine, tyrosine, and other groups in the polymerization process (8-10, 12-14, 16-18). It has been found that actin...